Colicin K has recently been shown to be amphiphilic and to act on bilayers of phospholipid as a voltage-dependent ion channel. The proposed research will examine the conformational change responsible for opening the channel, using colicin K in liposomes with a KC1 gradient and valinomycin to impose a membrane potential. Some modification of the colicin seems to happen in sensitive cells, and the possible role of this modificiation in creating a voltage-independent channel will be examined. The recovery of colicin-treated cells will be further investigated, particularly with respect to the role of the protein synthesized by recovering cells. Its possible association with the colicin and possible enzymatic action on colicin molecules will be tested, both by looking at the fate of colicin in recovering cells and by testing the effects of the recovery-specific protein in the liposome system. Antibody to colicin will be used to detect antigenically related proteins in SDS gels. It will also be used to precipitate complexes of colicin with other proteins, such as cellular proteins involved in colicin action or the recovery-specific protein. We have identified an antigenically related membrane protein in colicinogenic cells. Pulse-chase experiments will show if it is a precursor to colicin. Structural studies will show how it differs from colicin. We will also look for the mechanism by which it converted to the mature, secreted form.